The decision comes after the watchdog concluded that "prima facie" the deal could adversely impact competition in the markets concerned.

It is rare for the Competition Commission of India (CCI) to call for a public scrutiny of a deal.

Under the DuPont-Dow Chemicals transaction, both will be combined in an all-stock merger. For the deal -- which is expected to create the world's biggest chemical and material firm -- the parties had entered into a definitive agreement in December 2015.